At the present time, mercury vapor is provided in the gas atmosphere of all gas discharge display devices to minimize cathode sputtering. The mercury is introduced into such devices from a glass capsule held within the glass tubulation secured to the envelope. At a selected time in the manufacture of the panel, the glass capsule is shattered and mercury vapor enters the envelope through a hole therein. When such a mercury capsule is used with a flat display panel, the tubulation has to be specially shaped with a constricting portion to hold the mercury capsule in place. Such a tubulation is expensive.
In addition, in manufacture of the panel, first, the tubulation is sealed off below the mercury capsule, and then, after the mercury has been released therefrom, that portion of the tubulation is removed. This is an undesirable extra step in the manufacturing process.
In addition, with a glass capsule of this type, globules of mercury usually remain in the tubulation after the capsule has been opened, and some of this mercury can enter the panel through the hole in the envelope when the panel is handled, and such mercury can cause shorts inside the envelope.
A mercury capsule is known which comprises a metallic ring having a U-shaped cross-section and which carries a quantity of a mercury amalgam from which the mercury can be released by the application of heat. Such a mercury capsule is considerably cheaper than the glass capsule, and, as a result, it would be desirable to be able to use such a device; however, the carrier is too large for convenient use in tubulations. In addition, when such a carrier or capsule is mounted in a tubulation, it is in contact with the glass wall of the tubulation, and, when it is heated by RF energy, its heat subjects the tubulation to thermal shock, and the tubulation will generally crack.